Hydraulic drive mechanism for the thread guide rails of flat coulier knitting machines



June 7, 1960 F. KREIENBUHL ET AL HYDRAULIC DRIVE MECHANISM FOR THE THREAD GUIDE RAILS OF FLAT COULIER KNITTING MACHINES Filed Jan.- 13, 1959 5 Sheets-Sheet 1 am KREIENBUHL 'Ruloh INEICHEN INVENTORS June 7, 1960 F. KREIENBUHL ET AL 2,

HYDRAULIC DRIVE MECHANISM FOR THE THREAD GUIDE RAILS OF FLAT COULIER KNITTING MACHINES 5 Sheets$heet 2 Filed Jan. 13, 1959 i 55;: KREIENBUHL R M 5 T EN H mm A II 00 m 0. U R

June 7, 1960 F. KREIENBUHL ETAL ,939, 0

HYDRAULIC DRIVE MECHANISM FOR THE THREAD GUIDE RAILS 0F FLAT COULIER KNITTING MACHINES Filed Jan. 15, 1959 5 Sheets-Sheet 3 glam 3 a s m u: rm KREIENBUHL Rudd-F I NEICHEN INVENTORS June 7, 1960 F. KREIEN HL EI'AL 2,939,304

HYDRAULIC DR MECHANISM R THE THREAD GUIDE RAILS OF T COULIER KNITTING MACHINES Filed Jan. 13, 1959 5 Sheets-Sheet 4 l I l I i l w Fm KREIENBUHL ,g, Rulolf INElCHI-ZN k INVENTORS B WM, Jeni u- Afi's J1me 1960 F. KREIENBUHL ETAL 2,939,304 HYDRAULIC DRIVE MECHANISM FOR THE THREAD GUIDE RAILS 0F FLAT COULIER KNITTING MACHINES 5 Sheets-Sheet 5 Filed Jan. 13, 1959 \llllllllllllllllllllllllllllvll m. KREIENBUHL mow INEICHEN INVENTORS States HYDRAULIC DRHE RIECHANISM FOR THE THREAD GUIDE OF FLAT COULIER KNiTTlNG IVIACHINES Franz Kreienbuhl, Kloten, Zurich, and Rudolf Ineichen, Zurich, Switzeriand, assignors to Machine Tool Works Oerlikon, administration company, Zurich-Oerlikon, Switzerland The present invention relates to a hydraulic drive mechanism for the thread guide rails of flat Coulier knitting machines having piston rods driving the thread guide rails the ends of which are guided each in a cylinder open at one end and supplied alternately with a pressure fluid.

The invention has the primary object of providing a mechanism of this kind, wherein the excessive stresses and consequent quick wear of the abutments limiting the stroke of the said thread guide rails and of any adjustment devices thereof are obviated.

With this and other objects in view which will become apparent later from the following description of a preferred embodiment of the present invention given by way of example with reference to the accompanying drawings, we provide a hydraulic drive mechanism for the thread guide rails of flat Coulier knitting machines, comprising in combination: a frame, hydraulic cylinders open at one end mounted longitudinally slidably in said frame, hydraulic pistons having piston rods slidably fitted into the said hydraulic cylinders, means for supplying hydraulic pressure fluid selectively to the said hydraulic cylinders, thread guide rails slidably mounted in the said frame and operatively connected to the said piston rods, means for separately axially adjusting the said individual cylinders, and stops provided in the said cylinders limiting the stroke of the said thread guide rails by the said piston rods abutting the same.

Preferably our new mechanism comprises a frame having fixed horizontal bars, cylinder blocks slidably mounted on the said bars, hydraulic servo-motors operatively connected to the said frame and cylinder blocks, respectively, and in operation shifting the said cylinder blocks individually along the said bars, hydraulic cylinders open at one end and having inlets and outlets for the hydraulic fluid at the other end arranged in the said cylinder blocks, control valves hydraulically connected to the said hydraulic cylinders, abutments adjustably mounted on the said frame and operating the said control valves, hydraulic pistons having piston rods slidably fitted into the said hydraulic cylinders, thread guide rails slidably mounted on the said frame and operatively connected both to the said piston rods and to the said adjustable abutments, and stops provided in the said cylinders limiting the stroke of the said thread guide rails by the said piston rods abutting the same.

Preferably also a slider member is shiftably mounted on each of the said cylinder blocks which member has abutment faces spatially staggered and each co-operating with one of the said adjustable abutments. A throttling device arranged in the outlet for the hydraulic fluid expelled from each of the said hydraulic cylinders by the hydraulic pistons thereof running in; the said throttling device becoming efiective shortly before the end of the piston rod abuts the said stop in the said hydraulic cylinder. For example an extension of reduced diameter may be arranged at the inner end of each piston rod, and a 2,939,304 Patented June. 7, 1960 corresponding bore may be provided in the end face of the associated hydraulic cylinder into which the said extension runs towards the end of the inward stroke of the hydraulic piston into the said hydraulic cylinder, the said throttling device being then arranged in the drainage path of the hydraulic liquid from the said bore.

This arrangement provides an effective hydraulic damp ing device reducing the velocity of the reciprocating'inertia masses before their impact on their stops. A further feature of the invention consists in the manner of the axial adjustment of the cylinders relative to one another whereby the stroke of the thread guide rails and accordingly the width of knitting are determined. The actual position of the cylinders is likewise hydraulically adjusted through the said servo-motor control valves, so that the abutments controlling the same are stressed only by the comparatively low force of a spring biasing the said control valve, and do not undergo any wear worth mentioning.

These and other features of our said invention will be clearly understood from the following detailed description given with reference to the accompanying drawings, in which:

Fig. l is a longitudinal section on the line II of Fig. 2 of the drive mechanism as a whole; 9

Fig. 2 is a cross section on the line IIlI of Fig. 1;

Fig. 3 is a longitudinal section on a larger scale of a cylinder block with driving cylinder, servo-cylinder and abutment valve;

Fig. 4 is a section of the cylinder head of a driving cylinder with the damping device for the abutting piston;

Fig. 5 is a section of a control valve on the line V-'V of Fig. 6, and

Fig. 6 shows the driving device for the control valves.

The hydraulic drive mechanism for the thread carrier rods as a whole is fittedto the end of a normal flat Coulier knitting machine of which 1 represents one extreme transverse beam, 2 the second but extreme transverse beam of the frame, and 3 and 4, respectively, represent two longitudinal beams thereof. An auxiliary transverse beam 5 of the frame serves for journalling the shafts and bars of the drive mechanism to be described hereinafter in more detail. Reference numeral 6 denotes the shaft of the main eccentric of the machine which'is journalled in the usual manner in the transverse beams. The thread carrier rods '7 are mounted longitudinally slidably in holders 8 and are at one end rigidly connected to the piston rods 14 by means of connector lugs 9 (Fig. 3). The piston rods 10 are mounted at both ends in cylinders 11, which are closed at their outer ends by cylinder heads 12. Eight thread carrier rods 7 (Fig. 2) are provided in the machine of which each is connected to a piston rod 10 of its own. Each of these piston rods is mounted in two cylinders 11, and each cylinder 11 is arranged in a cylinder block 13. As shown in Fig. 2, eight such cylin der blocks 13 are grouped around the thread carrier rods 7 on each side. On the whole the drive mechanism comprises accordingly sixteen cylinder blocks 13, of which two are mounted axially slidably on each servomotor piston rod 14 (Fig. 1). These servo-motor piston rods 14 are in turn rigidly fixed in the transverse beams 1 and 5 of the frame.

Fig. 3 shows the construction of a cylinder block 13 on a larger scale, as well as diagrammatically the oil pumps, valves and oil pipes required for'its displacement and for the driving of the piston rod 10. The thread carrier rods 7 are driven by the periodical supply of pressure oil to one of the two cylinders 11, as will be explained in more detail hereinafter. The piston rod 10 is thereby pushed out of the cylinder, and accordingly moves the thread carrier rod 7. The limitation of the length of stroke of the piston rod 10 and accordingly of the thread carrier rod 7 is effected by the piston rod 10 abutting in the opposite cylinder on stops 12 in the cylinder head thereof. 11,1 ordertomake the; path .of the thread .carrier rods adjustable :at will, .as required for example in the manufacturingof stockings, thecylinder heads 12 are mounted hydraulically vshiftably on the servo-motorpiston itwo-tcontrollands a and b and'two guide lands and d. fIhe controllands. control the supply of oil to, and drain- .age from the oil ducts 23 and 24, respectively. The oil is sucked from acentral oil sump 26 by an electrically driven oil pump 25 and fed through a pressureypipe-ll When allowing a left hand side cylinder block 13 to run towards the associated right hand side cylinder block until the abutment 33 abuts the counter stop 33a, the piston rod 10 and with it the thread carrier rod 7 can move to-and-fro only onwa very-short path, which is important e.g. forv the production. of welts or splicings or of ct t v st ips a On the transverse beams 5 and 1, respectively, moreover rigid end abutments 4-5 and 46, respectively, for the slider member 39 are arranged, which are contacted by them when thecylinder :blocks '13 are in theirrest .posi- .tion andthe. associatedgthread.carrieiirods do notoperatc.

By the action of the servo-motor adjustmentde'vicefor the cylinder :blocks 13 the inertia forces occurring any time the piston rods 10 abuts the steps 12 are transmitted by the liquidscontainedin.thwcylinderspace '15 tothe servo-motor piston 18 and .by thescmomctor piston rod 14 to the machine frame. 'The abutment rings 38, 42

' mounted onthe spindles .39 and 4-3 .areloaded by the into :the space 21 between'the control lands a, b of'the cylindrical slide :valve 19. Depending on the .position thereof,.it fiowsthrough the duct 24-to the left hand side of the servo-motor cylinder 15, whereby the cylinder block'13 as a whole is shifted to the left, 'while the ;oil enclosed in the right hand side of the servo-motor cylinder flows back through theduct '23 and the return pipe '27 into .thesump 2,6, or it flows to the;right'ha ndside of .theservo-motoncylinder .15, whereby the cylinder block 13 moves to the right and the oil contained .in .the left :hand side half of the servo-motor cylindepfiows hack ithrough the duct 24 and pipe 27 into the sump .26. The valve bore 20 contains a spring 28 which tends to force the "cylindrical slide valve out of the bore; 20, i.e. from the locking position shown in Fig. 3 towards ithe'left.

The cylindrical ,slide valve 19. bearswith'itshead e against the tongue 29 of a slider member'30.f The latter is mounted slidably with a limited stroke parallel ;t ogthe cylinder slide valve 19.on the cylinder block 13. It has anumber of stepsofiset inspace the verticalfaces 31, 32, 33 of which serve as abutment faces. :On the cylinder block 13 moreover an electromagnet 34 ismountjed, which contains 'an axially movableplunger armature 35. An extension 35' of theplunger armature contacts thetongue .2 d e y QPPQ ite theP intQf contac o th -h ad e of th cy i r al slid a1 19- Ih ci fthc agnet .34 i onnected t e ircu t 6 containing eswitchifl The ma e o t oppo it sylindenis als nnected .(Figt t e same circu l he abutmen faces 3. hes id r member 3.0 cc- QPsrate with ,abutments 3 1a, which .arefixed'to abutment rings 38. The abutment rings 38 areguided by four spindles 39, which are rotatably journaIled in the transverse beams 1 and 5. The function of the-spindles. corresponds to that of the usual centre narrowingspindle of the machine. Oneach spindle 39 there is provided a right hand screw thread 41 and a left hand screw thread 40, which both engage into associated tappedJbores in the abutment ringsi38. Upon rotation of the spindles-39 the abutmentringsfiSand consequently the abntments. 31a app ach e w y f m. oneeno r, dependin on the-sense of rotation. The abutments 32a :are ads justed in exactly the same manner. Ihei'same -are ,-,a t= tached on abutment rings 42, which are in turn, guided .by f nr-sp d i h o shll sli ewise a.1ight;hand andal hande-screw th ad- I e-spindles43 operate in a manner corresponding to that of the conventional narr w n sp ndl si wi s ntc n. b remo e .wh ot n ded low force of the spring .28 of the cylindrical piston valve 19 .only, :and consequently are .not liable to substantial wear.

.The driving device. for the piston .rods .10 is designed as .follows: an oil-pump 51 driven by an electric motor '(Fig'. I) constantly feeds pressureoil through a-pipe 52 and pressure accumulators 53 to .acontrol valve .54. The cylindrical .slide'val-ve 55 (Figs. 3 and 5 is subject to the bias of a preloaded spring 5.6Which forces it comstantly againsta control eccentric 57, which is keyed to a control shaft .58, which in turn is in driving connection with the shaft 6 of the maineccentricof the machine through the gearing 53a, the shaft 58b and the gearing The controlieccentric'57 imparts to the slide valve 55a periodical to-and-fro movement so that the two control lands .fand g alternately clearthe discharge ports to the pipes 59 and 60,.respeotively, which pass pressure oil to the cylinder heads 12 andatthe same time-connect the'nonvpressurized.lines62and=63 with the overfiow into the oil sump 26. The. reciprocatin g movement of .theslide valve .55 is ,so determined thatthe tovand-fro movementsof the thread carrierrods 7 is carried-outin theexisting relationship to the othermovements of the machine. The supply of pressure oil and accordinglyathe rate, .at which the piston rod lfi is movedin the cylinder '11, may be regulated for example by anadjustable pressure reduction valve .61 tFig. 3 arranged in the lineSh.

Therun of the pistonrod 10 from one abutment-to the other takes ,place completely unhampei'ed-and ,as. quickly a t i pt ssureand o qu nt trpe i .Until the reversal of ;the, slide valve 55 vtheipistcui rod is forced .at anytime firmly against the stop-12. by the oil prcssure acting on the opposite end, so that it cannot perform any uncontrolled, movements. Each of the eight pairs of cylinders l l is provided with a control-valve 54, which may be switched on andoif as required.

An embodiment of {the switching on device .for the control valves 54- is illustrated by way of examplein the Figs. 5 and 6. 1

On the rotary control shaft 58 adjacent eachv control eccentric 57 aJcirc ular disc 65 .is mounted which reaches bell-fashionoverthe control eccentric .57. Theeccentries ,57 are .rigidly connected to the shaft 58, while "on the other hand the discs 65 can :be .axiallyshiftedon the shaft 58 while --rct.at ns with it, On the collar 66 of,the gl iscs 65 an annular groove 67 is machinedinto which two pins 68 engage, which'are fixed to the forked end of a two-armed lever 69. TIhe levers 69. are mounted-pivotally about a pivot pin 70fixed to the frame, and engage with their other ends into the slotted cams 71 of control discs 72,;-whi ch are in turn rigidly mounted on a control shaft 73. When the control shaft'73 is turned e.g. by hand,-the slottedcams' 71 impart a-rocking movement ofthe two-armed levers 69. Thereby the discs "65 are axiallyshifted a certain distance on the shaft 58. The gt qlitfi roams are ..so.;shaped, .that .the .discs .65 scan assume two end positions, either quite closely to the control eccentric 57 so that the bell-shaped flange 65' encloses the eccentric, or removed a certain distance from the eccentric so that the same stands free. The two end positions of the discs 65 are illustrated in Fig. 6.

On the cylindrical slide valve 55 two rollers 74 and 75 are mounted. The roller' 74 lies in alignment with the axis of the slide valve 55 and contacts the outer circumference of the eccentric '57 when the control valve concerned is switched on. The roller 75 is laterally offset from the axis of the slide valve and rests on the circular circumference of the disc 65, when the latter is in its end position remote from the eccentric 57. In this position the cylindrical slide valve is in its position corresponding to the largest stroke of the eccentric 57, i.e. in the position shown in Fig. 3, in which the pipe 60 is connected to the oil suply pipe 52.

'When a certain thread carrier rod is to be put in operation, the control shaft 73 is turned insuch a manner that the corresponding lever 69 shifts the disc 65 of the control valve ,54 concerned into the switching on position, in which it covers the eccentric 57. The spring 56 then forces the slide valve 55 against the eccentric 57, which drives the same through the roller 74. The putting out of action of a thread carrier rod is effected by turning the control shaft 73 in such a manner, that the disc 65 is removed from the control eccentric 57. The outer circumference of the flange 65 then reaches under the roller 75 and retains the slide valve 55 in its right hand side end position in which the duct 60 leading to the right hand side half of the cylinder 11 is permanently under pressure. The corresponding piston rod then can not move any longer but remains stationary at the stop 12' of the left hand side cylinder head 12. By the way, it should be mentioned that the control shaft 73 can be moved only when the shaft 58 rotates, since the discs 65 can be moved into the switching off positions only when the eccentric 57 forces the slide valve 55 into its right hand side end position.

An essential feature of the invention is the limitation of the thread carrier rod stroke or the stroke of the piston rods 10 driving the thread guide rails, respectively, by the heads of the piston rods abutting the end faces 12' of the cylinder heads 12. Since it isessential that the thread carrier rod should attain its end position without vibration, and that after the first impact of the piston rod 10 on the cylinder head no rebound may occur, the cylinder heads '12 are provided with a damping device for the abutting piston rod. Fig. 4 shows a cylinder head 12 on a larger scale. The piston rod 10 carries at its end a pin 100 of smaller diameter, which in turn has a conical taper 101 at its end. This pin engages into a bore 102 of the cylinder head 12 when the piston rod 10 runs into its end position. The bore of the cylinder 11 is enlarged at its juncture with the cylinder head 12, so that an annular space 103 is formed when the piston rod 10 is in its end position, as shown in Fig. 4. In this end position the piston rod 10 abuts with its shoulder 10' the face 12' of the cylinder head. In the cylinder head 12 two inclined bores 104 and 105 are provided, which connect the space 103 with two bores 106 and 107 issuing into the bore 102 of the cylinder head perpendicular to the axis of the piston rod. There issues also the oil duct 59 which establishes communication with the control valve 54. The bore 107 is obturated by a check valve 108 which permits only the supply of oil from the bore 102 into the space 103, but blocks the return flow of the oil in the opposite direction. The return flow of the oil from the space 103 into the bore 102 can, however, take place through the bores 104 and 106. The cross section area of the bore 104 is restricted by an adjustable throttle screw 109.

When now pressure oil enters into the bore 102 through the duct 59, the annular space 103 is immediately also put under pressure through the bore 107, check valve 108 and bore 105. Accordingly the entire cross section area of the piston rod 10. is put under pressure which contributes to a higher rate of acceleration thereof.

When on the other hand the piston rod 10 runs into the end position shown in Fig. 4 it pushes the oil contained in the bore of the cylinder directly into the bore 102 and into the duct 59, until the extension enters into the bore 102. Thereafter the oil contained in the space 103 has to flow back through the bores 104 and 106. This return flow of the oil is, however, hampered by the needle valve 109, and thereby the velocity of the piston rod running in is reduced. By adjusting the needle valve 109 the end velocity of the piston rod 10 running in can be controlled at will.

The damping of the piston rod running in may be solved structurally in'a somewhat simpler way, in that instead of the bores 104 and 106 in the cylinder head milled recesses 104' or grooves 106' are machined in the pin 100 which extend over the full length of the pin 100 up to or into the shoulder 10', or by adapting the clearance between the pin 100 and the bore 102. After the pin 100 running into the bore 102, the remainder of the oil is then forced from the cylinder bore through these milled recesses, longitudinal grooves or annular gaps into the space 102, whereby likewise a damping effect on the piston rod 10 is attained. This etfect is, however, not variable, but has to be adjusted by appropriate dimensioning of the milled recesses, longitudinal grooves or clearance, to match requirements.

Thefunctioning of the thread carrier rod drive mechanism is as follows: when a thread carrier rod 7 is to be put into action, the corresponding switch 37 is closed, whereby the two electromagnets 34 of the associated cylinder blocks 13 are energised, so that their plunger armatures 35 shift the slider member at the left hand side cylinder block towards the right, and at the'right hand side cylinder block towards the left, out of their locking position and against the bias ofthe spring 28, The pressure oil supplied by the pump 25 then flows at both cylinder blocks throughthe pipe 22, the space 21 and the pipe 23 to the inside of the servomotor cylinders 15, and the two cylinder blocks move towards one anotheruntil one of the abutment faces 31 or 32 of the slider member 30 abuts the corresponding stop 31a 0r 32a. Thereby the slider member 30 is pushed into its locking position illustrated in Fig. 3, and the cylinder blocks 13 come we standstill. The pressure oil supplied by the pump 25 then fiows through the pipe 22a and the excess pressure valve 44 back into the oil sump 26. When the spindles rotate, the abutment rings of which are in contact with the slider members 30 (in Fig. l the spindle 43 and the abutment ring 42) in such a manner that the abutment rings 42 move away from one another, the slider members 30, too, move with the abutment rings out of their locking position and the two cylinder blocks follow up the movement of the abutment rings. When conversely the spindles rotate in such a manner, that the abutment rings approach one another the plunger armatures 35 of the electromagnets 34 move the slider-members 20 out of their locking position, and the cylinder blocks 13 follow up the abutment rings, until their abutments have shifted again the slider member 30, and with it the cylindrical piston valve 19, into the locking position. However, the stops 31a and 32a on the left hand side abutment rings 38 and 42, respectively, may alternatively be put out of action by folding them down or removing them. It is then possible to move the left hand side cylinder block 13 towards the right hand side block until the abutment face 33 of the left hand side slider member 30 touches the stop 33a on the right hand side cylinder block 13, which is of importance for margin reinforcing thread carrier rods.

It is accordingly possible, to control selectively each of the eight thread carrier rods 7 at will, so that each '7 can be used 'for any manner of operation selected, for example asa ground thread carrier rod ort as a welt or splicing thread carrierrodJ i I i When a thread carrier rod has' tobe put out of action,

' the switch 374$ to be switc'hed ofl. The spring :28. then pushes the cylindrical slide valve '19 and with it the-slider member 30 and the plunger armature 35 out'of the locking position -shown-in*Fig. 3 towards the left. The pressure oil then flows through the duct 24 into :the left hand side cylinder space 15, and the-cylinder block 13 moves to the 'left until the slider member 30 abuts the end stop 45, and thereby moves 'the cylindrical s'lide valve1-9in'to its locking position. The right handside-cylindenblock 13 runs in exactly the same manner-to the right, until it'hasreached-the stop llie 7 "When after switching on the {switch 37 a pair of cylinf der blocks 13 bears in the'working position on the corresponding stops 31aor 3261, by arming-me shaft"7;3-into the appropriate working position the controlj'valve 554 co-operating with this pair of eylinde-r -blocks is switched on. The pressure oil supplied by the on pump-51 is then fed by the cylindrical slide valve 55 of the control-valve, in accordance with the run of the machine, alternately through the pipes 59 and 'dtmothetwo cylinder-heads 12, while the oil displaced by the'pist'on -rod running in rflovvs back to the oilsump 26-from that side of the cylinders,

'whichis actually noteunder pressureythroughthe ;pipes' 59f and 60, respectively,=the control valve t and the return pipes 62 and 63, respectively. 'The pressure accumulators are 'of the usual 7 construction and are consequently illustrated diagrammatically only. They 's'erve' in the known manner 'for storing the pressure'oill When-they are com: pletely filled, the excess -pressure valves 64 open, land :the

pump discharges through-the-pipe directly intothe oil sump 26. g 7' 7 'While We have herein-described and illus'tratedin the accompanying drawings what'may' be considered a typical and particularly use'ful embodiment ofour said'invention, we wish it to be'unde'rstood that wedo not limit ourselves to the particular details and dimensions described :and

illustrated; 'for obviousmodification will occur to a person skilledinthe art. 7

"What we claim as our invention and desire to secu re by LettersPatent'is: I I

' -1. A'hydraulic drive mechanism for thethread guide rails of fiat Coulier. knitting :inachines,.'-comprising in combination: a frame, hydraulic cylinders open at one end mounted longitudinally =slidably on said frame,;hydraulic pistons having piston rods slidably'fitted into the-said hydraulic cylinders, means for. supplyingrhydraulicspres sure fluid selectively to the-said hydraulic cylinders,

thread guide rails slidably mounted inthe saidi'ifrarne and operatively connected-to the said pistonrodsameans for separately axially adjusting the said individual ;cyli1i- 8 dew, and stops proVided' in -the said cylinders limiting the stroke of thesaidthread guide rails by thesaid piston rods abutting the said stops. a

'2. A hydraulic drive in'echanismfor the t-hread guide rails of flat Coulier knitting machines, comprising in combination: a frame having fixed horizontal bars, cylinder blocks slidably-mounted on the said bars, hydraulic-servomotors operatively connected to the saidframe and cylinder blocks, respectively, to shift the said cylinder blocks individually along the said bars, hydraulic cylinders open at one end and having inlets and outlets for the hydraulic fluid at the other end arranged in the said cylinder blocks,

control valves hydraulically connected to the said hydraulic cylinders, abutments adjustably mounted on the said frame and operating the. saidcontrol valves, hydraulic pistons having piston rods slidably fitted into the said hydraulic cylinders,' thread guide rails :slidably mounted on the said -frameand operatively connected to the said piston rods and regarding its stroke "dependent from the position of the said adjustable abutments, and stops provided in the said cylinders limitingihe stroke of the said thread guide rails by the said piston rods abutting the same. I

3. A hydraulic drive mechanism as claimed in claim 2, comprising a slider membershiftably mounted on each of the saidcylinder blocks and having abutment faces spatially staggered and cachco-operating with one 0 the said adjustable abutments;

4. A'hydraulic drive mechanism asclaimed inclaim 2, comprising a throttling device arranged in the outlet of the hydraulic fluid exp'elledirom each of thesaidhydraulic cylinders by the hydraulic pistons ther eof running in the said throttling device becoming effective-shortly before the end of the piston rod abuttingthe saidstop-in thesaidhydraulic cylinder. I

5. A hydraulic-drive mechanism-as'claimed in claim-4, comprising an extensioirof reduced diameter arranged 'at the inner end of each piston rod, a corresponding bore being provided in the end face-of the associate'd hydraulic cylinder into which the'said extensionruns nearthe-end ofthe inward stroke of thehydraulic pistoninto-the said hydraulic cylinder, the said throttling device being a1- ranged-in the drainage path of the hydraulic liquid .from the said bore. 1

i References Cited in the Jfile of this patent UNITED, SIAIESPATENTS WWW. 

